Gasoline treating process



Patented Jan. 27, 1953 GASOLINE TREATING PROCESS Ernest R. Quiram,Elizabeth, and John B. Lewis,

Cranford, N. J., assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application October 6, 1950, SerialNo. 188,874

8 Claims. 1

This invention concerns a novel process for improving the quality ofgasoline type petroleum fuels. In accordance with this inventionhydrocarbons boiling within the gasoline boiling range are subjected toa refining treatment consisting of contacting the gasoline with leadtetraacetate, This process is particularly applicable to the treatmentof cracked gasolines and is effective to materially improve what may becalled the engine cleanliness of the gasoline.

In the petroleum refining industry attempts are being made to providehigher quality gasoline fuels by altering characteristics of thegasoline resulting in the formation of engine deposits on combustion. Ithas particularly been found that gasoline produced by cracking processesha inferior burning characteristics as indicated by the condition of theengine after a period of use. Particularly in the case of crackedgasolines, Sludge forming constituents and constituents forming polymersor other materials, cause deposition of what is known as varnish in anengine. Consequently, at the present time efiorts are being made toimprove this particular characteristic of a gasoline fuel.

It is not yet understood which constituents of gasoline, or particularlywhich constituent of cracked gasolines, cause the problem of enginevarnish formation. However, it has now been found that in some manner,not entirely understood, after gasoline is treated with leadtetraacetate the quality of the gasoline is materially improved. It istheorized that the refinin effect of the lead tetra-acetate may be dueto the polymerization or condensation and removal of diolefins which areknown to be formed as the result of cracking operations.

In accordance with this invention therefore a gasoline is refined bytreating the gasoline with lead tetra-acetate. The conditions oftreatment are not particularly critical as the refinin effect apparentlyoccurs readily and rapidly. Thus it is entirely suitable to contact leadtetra-acetate with the gasoline to be refined at ordinary temperaturesand pressures for a period of about 45 minutes or less. In general,about 1 to 6% of lead tetra-acetate by weight, based on the gasoline, isto be employed. As a result of this treatment, a precipitate is formedwhich must be removed from the gasoline to provide the finished gasolineproduct. The precipitate elimination may be conducted in any desiredmanner such as by settling, filtration, or centrifuging. However, it isparticularly preferred that the gasoline be freed of precipitate bydistilling the gasoline to permit recovery of the finished gasoline asan overhead product.

In order to fully disclose the nature of this invention and to exemplifythe conduct of the invention the following examples are presented. Inthese examples the evaluation of the gasoline be fore and aftertreatment as regards the engine cleanliness of the gasoline are reportedin terms of the fluoborate deposit factor. This deposit factor isdetermined in a laboratory test found to correlate with actual enginecleanliness determinations. The test utilizes the coupling reactionwhich takes place between diazotised pnitroaniline and certainunsaturated compounds (which cause engine fouling) to form a coloredcompound. Intensity of color formed after a given time interval is anindex of the deposit forming compounds present. In running the test thefraction of the sample boiling over 275 F. and purified by treatmentwith dilute acid and alkali and steam distillation to 3% bottoms isused. A known quantity of this fraction is added to a solution of'p-nitroaniline diazonium fluoborate (NO2CsH4N=NBF4) in acetone, and theoptical density measured at intervals in a Hellige- Diller emissionphotometer. The optical density is plotted against time and the valueafter 20 minutes read from the curve. The optical density multiplied bythe ratio of the fraction boiling over 275 F. to the whole sample, givesthe diazonium fiuoborate deposit factor.

Example I A sample of naphtha obtained by the thermal cracking of a gasoil fraction was subjected to treatment with lead tetra-acetate. Thenaphtha tested boiled in the range of about 136 to 423 degrees F. andhad the following inspections:

Engler distillation:

Initial boiling point F 136 Mid boiling point (50% distilled) FL. 275

Final boiling point F 432 A. P. I. gravity 48.8 Gum (G. M.) mg 26.0Bromine number 34.1 A. S. T. M. motor octane number 72 CFR octane numberThe treatment consisted of mixing cc. of the naphtha with 3.7 gms. oflead tetra-acetate. The mixture was maintained for 45 minutes at roomtemperatures and pressure. At the end of this time a white precipitatehad formed which was filtered from the gasoline. Samples of the naphthacorresponding to the naphtha before and after treatment were thensubjected to the diazonium fiuoborate deposit factor test. It was foundthat the optical density of the naphtha before treatment was 0.688 whileafter treatment the optical density had been decreased to 0.108,indicating a material improvement in the quality of the thermal naphtha.

Example 11 A sample of commercial gasoline boiling in the range of 95 to405 degrees F. and having the following inspections was treated withlead tetraacetate:

Engler distillation:

Initial boiling point F" 95 distilled F 1'76 distilled F 212 distilled E266 Final boiling point F 405 A. P. I. gravity 60.5 Reid vapor pressure8.4 Bromine number 26.4 A. S. T. M. octane No C. F. R. octane No 31 Inthis case 300 cc. of the gasoline were mixed with 10 gms. of leadtetra-acetate for a period of 45 minutes. Thereafter the resultingprecipitate was filtered and the gasoline was tested. On testing it wasfound that the original gasoline had a deposit factor of 19.80, whileafter treatment the deposit factor was 4.52. These data again bear outthe material improvement in engine cleanliness of the gasoline obtainedby the lead tetra-acetate treatment. It is particularly notable thatthis improvement was obtained by treating a base gasoline consisting ofa mixture of virgin gasoline, catalytically cracked gasoline, and othergasoline components.

Example III Thermal naphtha of the same nature as that identified inExample I was subjected to the identical lead tetra-acetate treatment.In this case however, tests were conducted to determine the gum contentof the gasoline before and after treatment as indicated by ASTM Test D381-l9. It was found that the thermal naphtha before treatment had anASTM gum content of 168 mg. per 100 ml. However, after leadtetra-acetate treatment the AS'IM content of the naphtha had increasedto 244.2 mg. per 100 m1. This thermal naphtha was therefore subjected toa distillation operation in which the gasoline was removed as theoverhead product. In distilling the gasoline to permit recovery of ofthe gasoline, it was found that the ASTM gum content of the gasoline wasreduced to only 3 mg. per ml. This example particularly shows thedesirability of following the lead tetra-acetate treatment with adistillation operation in which the gasoline is distilled to free thegasoline from precipitate formed during the treatment and from gumforming constituents which remain behind as a bottoms product. It isapparent that the distillation may be carried out to recoversubstantially all of the gasoline, since the data indicates that a thegum forming constituents are selectively retained during distillation asstill bottoms.

As indicated therefore, the process of this invention comprises treatinggasoline with about 1 to 6% by weight of lead tetra-acetate. Asindicated, the treatment may be conducted at ordinary temperatures andpressures or if desired, at higher temperatures and pressures; dependingon the refining eiTect desired. The time of reaction may be varied froma maximum of about 45 minutes down to any desired lower limit ofcontacting. After lead tetra-acetate treatment, if desired, theresulting precipitate may be removed by filtration or the equivalent toprovide the finished gasoline. However, when it is desirable tosimultaneously lower the gum content of the gasoline, it is particularlycontemplated that the treated gasoline be subjected to distillation.

What is claimed is:

1. The process for refining a gasoline consisting of contacting gasolinewith a small percentage of lead tetra-acetate and thereafter separatingthe gasoline from the resulting precipitate.

2. The process defined by claim 1 in which about 1 to 6% of leadtetra-acetate, based on the weight of the gasoline, is employed.

3. The process for improving the ality of a gasoline comprising thesteps of in' a LA "n about i to 6% of lead tetra-acetate with the saidgasoline for a period less than about 45 minutes, whereby a precipitateis formed, thereafter separating the said gasoline from the saidprecipitate.

4. The process defin d by claim 3 in which the said separation iscarried out by filtration.

5. The process of claim 3 in which the said separation is carried out bycentrifuging.

6. The process defined by claim 3 in which the said separation iscarried out by distillation.

7. The process defined by claim 3 in which at least a part of the saidgasoline constitutes a cracked gasoline.

8. The process for improving the quality of a hydrocarbon mixtureboiling in the gasoline boiling range consisting of maintaining themixture in contact with about 1 to 6% of lead tetraacetate for a periodof not more than about 45 minutes, and thereafter subjecting the mixtureto a distillation operation in which at least about 95% of the gasolineis removed as an overhead product.

ERNEST R. QUIRAM. JOHN B. LEV/IS.

REFERENCES GETED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 81,071 de Gerbeth Aug, 18, 1868400,633 Cazin Apr. 2, 1889 1,394,987 Fleming s Oct. 1921 1,823,558 Burkei Sept. 15, 1931 FOREIGN PATENTS Number Country Date 153,585 GermanyJuly 21, 1904

1. THE PROCESS FOR REFINING A GASOLINE CONSISTING OF CONTACTING GASOLINEWITH A SMALL PERCENTAGE OF LEAD TETRA-ACETATE AND THEREAFTER SEPARATINGTHE GASOLINE FROM THE RESULTING PRECIPITATE.